PRESSURELESS SINTERING AND HIPING OF INHOMOGENEOUS CERAMIC COMPACTS

This paper examines the evolution of microstructure in inhomogeneous b odies during pressureless sintering and HIPing. A two state variable m odel recently developed by the authors [Z. Z. Du and A. C. F. Cocks, A cta metall. 40, 1969 (1992)] is used to analyse the response of a syst em containing a distribution of ellipsoidal inclusions. The influence of cracks on the sintering response is also examined and the condition s are identified that favour the nucleation and propagation of cracks within the compact. It is demonstrated that cracks are more likely to nucleate during HIPing, but as the material densifies these cracks ten d to heal-up. If the cracks form during pressureless sintering, they p ropagate steadily as the material densifies and remain in the componen t after sintering.